CombineShoppingCartTests.swift

CombineShoppingCartTests.swift

//
//  CombineShoppingCartTests.swift
//  CombineShoppingCartTests
//
//  Created by Piotr on 25/03/2020.
//  Copyright © 2020 Piotr. All rights reserved.
//

import XCTest
import Combine
@testable import CombineShoppingCart

fileprivate extension Product {
    static let apple = Product(id: 1, name: "🍎", price: 5.0)
    static let beer = Product(id: 2, name: "🍺", price: 10.0)
}

class CombineShoppingCartTests: XCTestCase {
    
    private var cart: ShoppingCart!
    
    override func setUp() {
        self.cart = ShoppingCart()
    }
    
    func triggerCartActions(_ actions: CartAction...) {
        Publishers.Sequence<[CartAction], Never>(sequence: actions)
            .receive(subscriber: cart.input)
    }

    func testInsertingProduct() {
        let expectation = XCTestExpectation(description: "Inserting new product")

        let cancellable = cart.orders
            .sink(receiveValue: { (orders) in
                XCTAssertEqual([ProductOrder(product: .apple, quantity: 1)], orders)
                expectation.fulfill()
        })
        
        triggerCartActions(.insert(product: .apple))

        wait(for: [expectation], timeout: 5.0)
    }
    
    func testIncrementingProduct() {
        let expectation = XCTestExpectation(description: "Incrementing existing product")
        
        let cancellable = cart
            .orders
            .sink { (orders) in
                if orders.contains(ProductOrder(product: .beer, quantity: 2)) {
                    expectation.fulfill()
                }
        }
        
        triggerCartActions(
            .insert(product: .apple),
            .insert(product: .beer),
            .incrementProduct(withId: Product.beer.id)
        )
        
        wait(for: [expectation], timeout: 5.0)
    }
    
}

This is amazing.

There's a problem in your solution.

if you separate action into two part rather than chaining, the second will not apply at all.

// origional

 triggerCartActions(
            .insert(product: .apple),
            .insert(product: .beer),
            .incrementProduct(withId: Product.beer.id)
        )

change to

 triggerCartActions(
            .insert(product: .apple)
        )

// insert  and incrementProduct does not happen at all
 triggerCartActions(
            .insert(product: .beer)
            .incrementProduct(withId: Product.beer.id)
        )